Process for treating stone and like material.



lated surface.

UNITED STATES FATE orrro r HENRY WILLIAM HEMINGWAY, OF HAMPSTEAD, ENGLAND.

PROCESS FOR TREATING STONE AND LIKE LTATERIAL.

No Drawing.

To all whom it may concern.

Be it known that I, HEXRY \VILLIAAL Hmnxowar, a subject of the King of Great Britain, residing at No. 9 Albemarle Mansions, Heath Drive, Hampstead, in the county of Middlesex, England, have invented new and useful Improvements in Processes for Treating Stone and Like Materials, of which the following is a specification. i

This invention relates to a process of treating such materials as natural or artificial stone, chalk, stucco and similar substances which may be used for building and analogous purposes, with the object of preserving them or protecting them from the effects of weathering or otherwise rendering them more suitable for the purposes to which they are 'to be put.

The process is based on the reactions of arsenic acid with alkaline silicate (usually sodium silicate), by which silica is deposited in the pores of the material under treatment, or throughout the cement, and with the :base or bases of the material to form an insoluble compound of great stability intimately mixed with the silica.

The treatment process involves two operations which may be carried out as follows The surface of the material'is washed over with a solution of arsenic acid, of a strength which may vary within wide limits according to the conditions. A solution of a specific gravity of 1.15 may be taken as suitab e for ordinary purposes. The effect of this is to form an insoluble compound with the base of the material, and in the case of limestone or other carbonate, to drive off carbonic acid from the surface layer. The surplus acid not taken up by the base reacts with the second material, which is a solution of alkaline silicate washed over the already acidu- The silicate is decomposed and free silica is deposited in the pores of the stone,- where it hardens and protects the surface of the stone from attack by the acids of the atmosphere and rain. The alkaline compound formed and any surplus material can be washed off. The silicate "should be sufficient to neutralize the remaining acid and I find that for solutions of equal density a volume of silicate solution equal to about three times the volume of the acid forms Specification of Letters Patent.

Patented July 15, 1.913.

Application filed December 5, 1911.. Serial No. 664,469.

a suitable proportion for ordinary preservative work on the surface of stone and like material, but the best proportion varies somewhat with the depth of decay and other conditions. I

hen applied to solid surfaces, such as those of soot stained buildings, carvings, sculpture and the like, formed of material suitable for the application of my process, the process not only preserves the material from further attack by the atmosphere, but also cleanses it, the surface chemical action throwing off any sooty or other deposit and leaving the stone, stucco or other surface clean.

I may reverse the order of operations given above, and in the first place fill the pores of the material with a solution of alkaline silicate, then adding the arsenic acid. which must be in such quantities as to decompose the silicate and also to form an in soluble arsenate with the base of the stone.

The reaction involved may be illustrated broadly by the following equation 3CaCO +Nu4Si04+6H AsO4= The calcium arsenate and the silica remain as-insolublematerials while the carbonic acid escapes and the sodium carbonate can be removed by washing or left to be subsequently removed by the action of rain.

The treatment is applicable not; only to building materials already in use, but may equally well be applied to stone and like material before building so as to render it more resistant and durable and also in some cases to extend its utility. Treated chalk, for example, may be colored and polished.

The chalk treatment may be applied on a' large scale in railway cuttings, on cliffs and.

acid deposits silicain. the pores of'the Inaof arsenic acid in excess, which excess forms I 10 terial and simultaneously forms an insoluble With the base of the material an insoluble. arsenate in intimate contact with the silica. arse'nate in intimate contactwith the silica.

2, A processfor the preservative treat- In testimony whereof Iafiix my signature I :5 ment' of material containing a basic subin the presence of two witnesses.

stance, consisting first filling the pores of HENRY WILLIAM EEMINGWAY the material to any desired depth with a Witnesses: solution ofalkaline silicate and in then dei Y W. H. DQRMER, positing the silica; in the pores by a solution J AS. BRAGG.

Copies of this petemt may be obtained for five eents eaeh, by addressing the Commissioner of Patents,

Washington, D. 0. i 

